The present invention relates to methods for monitoring the performance and efficiency of a multi-effect evaporator system by independently monitoring the efficiency for each effect. The invention also provides a method for determining a solid or nonvolatile content in a liquid from each effect of the system.
The concentration of large volumes of liquid is an important industrial process in several industries, including the pulp and paper, the chemical industry, and the food industry. Concentration generally involves removing a portion of the volatile content of a liquid, the liquid also having a solid or nonvolatile content, by heating the liquid solution and evaporating a portion of the volatile content. Because of this heating step, the concentration process can involve high energy usage with resulting high costs.
A typical industrial system for evaporating large amounts of volatiles from a liquid is a multi-effect evaporator which has a number of interconnected evaporator units, each termed an xe2x80x9ceffect.xe2x80x9d In a typical multi-effect evaporator system, when a liquid solution fed to a first effect is heated, the heat from the resulting vapor is used to heat the liquid in a subsequent effect. As the number of effects increases, the relative energy required to concentrate a proportional amount of liquid decreases considerably. There is a practical limit to the number of effects used and the number is balanced by factors such as pressure drop, space and cost.
Energy efficiency and performance can be enhanced if the liquid to be concentrated is contained in tubing within the heat transfer portion of the evaporator effects. This is due to increased surface area of the liquid exposed to heat transfer. This tubing, however, can be prone to plugging or fouling that can result in a decrease in energy efficiency, performance, or even a complete shutdown of the system. Currently the applicant knows of no method, that is simple and effective, to automatically isolate which effect or effects of a multi-effect system are most responsible for a loss in energy efficiency or performance. With commonly used methods, a user is typically required to inspect the entire system to locate the problem.
There are many applications requiring that a large amount of liquid be evaporated to yield a liquid product with a desired final concentration. Determination of operating conditions to achieve this concentration typically can be difficult and/or time consuming. Such a determination also typically assumes that the system operates at a particular efficiency and does not factor in the consequences of efficiency loss. Thus, as the evaporators lose efficiency, the production rate typically decreases. A method to quantify an efficiency and/or a concentration of nonvolatiles in the liquid solution for each effect during the evaporation process could provide a convenient method for monitoring system operation, thus leading to an increase in the ease of operation and efficiency/performance of the system.
Because multi-effect evaporators can consume large amounts of heat and steam energy, there remains a need in the art to increase the energy efficiency and performance of such evaporators, and to provide a relatively simple, effective, and inexpensive means to monitor the efficiency and performance.
One aspect of the invention provides a method involving an evaporator system. The system includes at least two effects, each effect containing a liquid comprising a volatile and a nonvolatile content. At least one effect is provided with an inlet vapor supplying a heat energy sufficient to cause the liquid in the effect to boil to form an outlet vapor. Vapor and liquid temperatures are obtained from at least one effect and an efficiency of at least one effect is determined from the obtained temperatures.
Another aspect of the invention provides a method involving an evaporator system.
The system includes at least two effects, each effect containing a liquid comprising a volatile and a nonvolatile content. At least one effect is provided with an inlet vapor supplying a heat energy sufficient to cause the liquid in the effect to boil to form an outlet vapor. Vapor and liquid temperatures are obtained from at least one effect, and a total nonvolatile content in the liquid from at least one effect is determined from a vapor and a liquid temperature of the effect.
In one embodiment, the invention provides a method involving an evaporator system. The system includes at least two effects, each effect containing a liquid comprising a volatile and a nonvolatile content. The method involves determining at least one vapor temperature and at least one liquid temperature for at least one effect, using the temperatures to determine a heat transfer coefficient for at least one effect, and inferring an efficiency for at least one effect from the heat transfer coefficient.
In one aspect, the invention provides a method involving an evaporator system. The system includes at least two effects, each effect containing a liquid comprising a volatile and a nonvolatile content. The method involves determining at least one vapor temperature and at least one liquid temperature for at least one effect, using the temperatures to determine a boiling point rise for each effect, and determining a nonvolatile content of a liquid in at least one effect from the boiling point rise.
In another embodiment, the invention provides a method involving an evaporator system. The system includes at least two effects, each effect containing a liquid comprising a volatile and a nonvolatile content. The method involves determining at least one vapor temperature and at least one liquid temperature for at least one effect, and using the temperatures to determine both an efficiency and a nonvolatile content of a liquid for at least one effect.
In another embodiment, the invention provides a method involving an evaporator system. The system includes at least two effects, each effect containing a liquid comprising a volatile and a non-volatile content. The method involves determining a heat transfer coefficient for at least one effect during operation of the system and determining an efficiency for at least one effect from the heat transfer coefficient.
In another aspect, the invention provides a method involving an evaporator system, which includes at least two effects, each effect containing a liquid comprising a volatile and non-volatile content. The method involves determining a heat transfer coefficient for at least one effect during the operation of the system and detecting a fouling condition for at least one effect from the heat transfer coefficient.
In another embodiment, the invention provides a method involving an evaporator system, which includes at least two effects, each effect containing a liquid comprising a volatile and a non-volatile content. The method involves obtaining vapor and liquid temperatures from at least one effect and detecting a fouling condition for at least one effect from the obtained temperatures.
In yet another embodiment, the invention provides a method. The method involves obtaining vapor and liquid temperatures from each effect of a multi-effect evaporator system and detecting which effect in the multi-effect evaporator system exhibits a fouling or plugging condition from the obtained temperatures.
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention.